Arrest made by head of security in front of tent (4)
I believe the answer is:
Here is my best explanation:
'arrest' is the definition.
('stop' can be a synonym of 'arrest')
'head of security in front of tent' is the wordplay.
'head of' suggests taking the first letters.
'in front of' means one lot of letters go next to another.
'tent' becomes 'top' (top is a kind of tent).
The first letter of 'security' is 's'.
'made by' is the link.
(Other definitions for stop that I've seen before include "It could be the organist's principal", "Don't allow", "block", "plug", "Finished", "Close < finish", "part", "Whoa, cease", "Knock out" and "Hold on".)